1. Field of the Invention
The present invention relates to a communication terminal apparatus and a communication conference system, which allow easy schedule adjustment between communication terminal apparatuses.
2. Related Background Art
Digital communication lines have been popular recently, and a great deal of attention has been given to a TV telephone/conference system using a digital line network. Standardization is a prerequisite for the popularization of a communication system. There are five recommendations as to video and voice communications, namely recommendation H. 221 specifying the frame structure of 64 kbit/s to 1,920 kbit/s channels; recommendation H. 230 specifying a control signal for frame synchronization and a notification signal; recommendation H. 242 specifying an interconnection procedure up to 2 Mbit/s; recommendation H. 261 specifying a video coding scheme for P.times.64 kbit/s (P=1 to 30); and recommendation H. 320 specifying the arrangement of a voice/video communication system.
FIG. 6 is a block diagram showing the schematic arrangement of a conventional TV conference terminal apparatus. Referring to FIG. 6, this apparatus includes a video camera 10 for photographing, e.g., participants in a conference at a self station, a monitor 12 for displaying images photographed at the self station and/or stations participating in a conference, a speaker 14, a microphone 16, an operation unit 18 for performing control, e.g., panning, tilting, and zooming, of a camera 10 in a self station and cameras in other stations, switching control of the cameras, and the like, input/output equipment terminals 20 including a keyboard of a computer, a still picture input device, a pointing device for inputting plotting pictures, such as a mouse or digitizer, a sub-monitor for displaying images from other auxiliary equipment, and a main body 22 of the TV conference system.
FIG. 7 shows the detailed arrangement of the main body 22. Referring to FIG. 7, a video I/F 30 serves to connect the camera 10 and the monitor 12 to the main body 22. The video I/F 30 has image processing functions of performing screen division, image synthesis, character synthesis, and the like. A video coder/decoder (CODEC) 32 codes a video signal from the video I/F 30 and decodes received coded video information.
A voice I/F 34 serves to connect the speaker 14 and the microphone 16 to the main body 22, and has voice processing functions such as an echo cancel function. A voice coder/decoder (CODEC) 36 codes a voice signal from the voice I/F 30 and decodes the received coded voice information. A delay circuit 38 delays coded voice information obtained by the voice CODEC 36 and received coded voice information by a predetermined period. The delay circuit 38 serves to synchronize voice information to video information.
A computer 40 provides a TV conference function and a computer conference function. A still picture/plotting picture control circuit 42 controls the still picture input/output operation and plotting picture input/output operation of the auxiliary input/output equipment terminal 20. A data port 46 performs data transfer between the main body 22 and the auxiliary input/output equipment terminal 20 via the computer 40, the still picture/plotting picture control circuit 42, and an auxiliary equipment control circuit 44.
An interconnection procedure control circuit 48 controls interconnection with other TV conference terminals via a network. A network signal control circuit 50 performs end/end control to establish a common mode for communications between terminals. A communication control circuit 52 performs overall communication control by using the interconnection procedure control circuit 48 and the network signal control circuit 50.
A multiplexing and demultiplexing circuit 54 performs multiplex transmission of data. A network I/F 56 serves to connect a communication network 58 to the main body 22. An inter-multipoints control circuit 60 interconnects TV conference terminals at multiple points to allow a TV conference between the multiple points. An operation unit input I/F 62 receives various commands from the operation unit. An input control unit 64 outputs a command to each component of the self station in accordance with a designation of the operation unit input I/F 62.
When a conference is to be held by using a communication conference system such as the TV conference system described above, schedule adjustment between communication terminals must be performed.
More specifically, the communication terminals negotiate with each other about the date of the conference and the time which can be spared for the conference, thereby performing schedule adjustment. If, however, an international conference is to be held, the working days and hours in each country participating in the conference, time differences, and the like must be considered. In this case, mistakes tend to occur. Especially when terminals belonging to a plurality of countries participate in a conference, communications for schedule adjustment alone cost a great deal.